CN113371912B - Magnesium sulfate crystallization separation process in CLT acid high-salinity wastewater - Google Patents
Magnesium sulfate crystallization separation process in CLT acid high-salinity wastewater Download PDFInfo
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- CN113371912B CN113371912B CN202110676957.8A CN202110676957A CN113371912B CN 113371912 B CN113371912 B CN 113371912B CN 202110676957 A CN202110676957 A CN 202110676957A CN 113371912 B CN113371912 B CN 113371912B
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C02F9/00—Multistage treatment of water, waste water or sewage
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- C01F5/40—Magnesium sulfates
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Abstract
The invention relates to a magnesium sulfate crystallization separation process in CLT acid high-salt wastewater, which comprises the following steps: (1) performing nanofiltration adsorption separation on the CLT acid high-salt wastewater; (2) carrying out chemical precipitation reaction on the separated wastewater to remove impurities; (3) carrying out thermal evaporation, concentration and crystallization on the treated wastewater; (4) carrying out recrystallization treatment on the crystal after thermal evaporation, concentration and crystallization; (5) and because the solvent after the concentration and crystallization is also doped with part of solute, the solvent is subjected to post-treatment and recycling or is put into the system again. The method integrates the processes of adsorption separation, impurity removal treatment, evaporation concentration, crystallization and evaporation recovery, can effectively treat the problem of wastewater generated by a toluene sulfonation method, recycles magnesium sulfate in the wastewater, and solves the problems of high purity, crystal morphology and uniform particle size of the prepared magnesium sulfate, low evaporation failure in the evaporation process, low purity of a crystallization product and low precipitation effect, and is easy to realize large-scale production.
Description
Technical Field
The invention relates to a crystallization and separation process for magnesium sulfate in CLT acid high-salinity wastewater generated by a toluene sulfonation method.
Background
At present, the synthesis method of the CLT acid is numerous, but at present, the toluene sulfonation method is widely used for preparing the CLT acid industrially, the method takes toluene as a raw material, and materials such as sulfuric acid, magnesium oxide, sodium chloride, iron powder and the like need to be added in the reaction process to finally synthesize the CLT acid. However, the production of a large amount of CLT acid results in a large amount of serious high-salt organic wastewater, the wastewater contains a large amount of sulfate, impurity ions, intermediate products and other organic matters, the environment is greatly damaged if the wastewater is directly discharged or discharged without advanced treatment, and the sulfate in the wastewater has the significance of resource recycling.
The traditional CLT acid high-salt organic wastewater treatment mode is a biochemical treatment method, firstly, microorganisms are used for degrading and adsorbing organic matters in wastewater, after COD and BOD are reduced, a chemical precipitation method is used for precipitating salts in the wastewater. However, the biochemical method not only has complex process and more working procedures, but also has higher treatment cost and poorer treatment effect. The microorganism can be influenced by salt tolerance, new elements can be added into the wastewater by a chemical precipitation method, the resource waste of sulfate can be caused, and the requirement of resource recycling is not met.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: in order to overcome the defects in the prior art, the invention provides a magnesium sulfate crystallization separation process for CLT acid high-salt wastewater, which realizes zero emission after CLT acid high-salt wastewater treatment and recycles a large amount of magnesium sulfate contained in the wastewater.
The technical scheme adopted by the invention for solving the technical problems is as follows: a magnesium sulfate crystallization separation process in CLT acid high-salinity wastewater comprises the following steps:
s1, performing nanofiltration adsorption separation on the CLT acid high-salt wastewater, and separating and recycling CLT acid macromolecular organic matters and partial intermediate products in the high-salt wastewater by adopting an activated carbon nanofiltration membrane;
s2, converting the residual impurity ions in the separated wastewater into other precipitate substances by a chemical precipitation method;
s3, carrying out thermal evaporation, concentration and crystallization on the wastewater after chemical precipitation treatment to obtain crystals with the average particle size of 294 mu m and the dispersion of 2;
s4, recrystallizing the crystals subjected to thermal evaporation concentration to improve the purity, wherein the obtained crystals have the granularity of 146 mu m and the dispersion degree of 1.42;
and S5, carrying out post-treatment recycling or putting the solvent doped with partial solute after concentration and crystallization into the system again.
Specifically, in step S3, the evaporation temperature during thermal evaporation and concentration is 60 ℃, the cooling rate is 0.2 ℃/min, the PH is 3, and the rotation speed is 200 r/min; in the step S4, the concentration ratio adopted during recrystallization is 1.6, the residence time is 40min, the rotation speed is 200r/min, and the content of the seed crystal is 3 g/L.
The beneficial effects of the invention are: the method can effectively treat the problem of the wastewater generated by the toluene sulfonation method, and recycle the magnesium sulfate in the wastewater; the method integrates the processes of adsorption separation, impurity removal treatment, evaporation concentration, crystallization and evaporation recovery, can be continuously and stably operated, solves the problems of evaporation failure and low purity and precipitation effect of crystallized products in the evaporation process, is easy to realize large-scale production, and has high separation purity and good energy-saving effect.
Drawings
The invention is further illustrated with reference to the following figures and examples.
FIG. 1 is a schematic process flow diagram of the present invention.
Detailed Description
The present invention will now be described in further detail with reference to the accompanying drawings.
As shown in fig. 1, a process for separating magnesium sulfate from CLT acid high-salt wastewater by crystallization comprises the following steps:
s1, performing nanofiltration adsorption separation on the CLT acid high-salt wastewater, and separating and recycling CLT acid macromolecular organic matters and partial intermediate products in the high-salt wastewater by adopting an activated carbon nanofiltration membrane;
s2, carrying out chemical precipitation reaction on the separated wastewater to remove impurities due to residual iron ions, chloride ions and other impurity ions in the wastewater, and converting the residual impurity ions in the wastewater into other precipitate substances by a chemical precipitation method;
s3, carrying out thermal evaporation concentration on the wastewater after impurity removal treatment, and crystallizing under the conditions that the evaporation temperature is 60 ℃, the cooling rate is 0.2 ℃/min, the pH value is 3 and the rotating speed is 200r/min, so that the crystallization is more energy-saving and efficient, the average particle size of the obtained crystals is 294 mu m, and the dispersion is 2;
s4, because the crystal slurry after thermal evaporation concentration crystallization is low in purity and is mixed salt and cannot meet industrial requirements, recrystallization is carried out on the crystal to improve the purity, so that the crystal is more uniform, the recrystallization conditions are that the concentration ratio is 1.6, the retention time is 40min, the rotating speed is 200r/min, the content of the seed crystal is 3g/L, the particle size of the crystal obtained according to the conditions is 146 mu m, the dispersion is 1.42, the particle size is lower, and the distribution is uniform;
s5, because the solvent after concentration and crystallization is also doped with partial solute, the solvent can be post-treated and recycled or put into the system again.
By adopting the technical scheme, in the crystallization process, as the PH value of the wastewater is 6.5-7.5, the PH value of the mixed solution is widened relative to a neutral metastable zone in the acidic process, and hydrolysis reaction is carried out under the acidic condition to inhibit precipitation; at the moment, the stirring speed is increased, the turbulence degree of the system is increased, and the metastable zone is narrowed, so that the precipitation can be promoted; and because iron ions rich in the wastewater can narrow the metastable zone of the CLT acid high-salt wastewater, the more the iron content is, the higher the crystal precipitation efficiency is, and the energy is saved.
By adopting the technical scheme, the existence of organic matters in the wastewater can cause the crystallization to have impurities, so that the chromaticity is high and the requirement is not met. Therefore, impurity removal treatment is firstly carried out to remove organic matters, then crystallization is carried out, when the crystallization condition is that the concentration ratio is 1.6, and the retention time reaches 40min, the crystal growth is completed, the resource is utilized to the maximum, but at the moment, the average grain size of the crystal is 294 mu m, the dispersion degree is 2, the distribution is uneven, and the grain size is higher, so recrystallization is required. In the recrystallization process, along with the increase of the stirring speed, the granularity of the product crystal is increased and then reduced and then tends to be stable; meanwhile, 3g/L of seed crystal is added, so that the average particle size is reduced, the purity of the finally separated magnesium sulfate crystal can reach over 96 percent, the crystal particle size is 146 mu m, the dispersion is 1.42, the particle size is lower, and the distribution is uniform.
The toluene sulfonation method needs a large amount of sulfuric acid acidification and excessive salting-out, so a large amount of waste liquid containing magnesium ions, sodium ions and sulfate ions, including waste acid, waste iron mud, organic impurities and the like, can be generated, the process can effectively treat the problem of the waste water generated by the toluene sulfonation method, and the magnesium sulfate in the waste water can be recycled. The process integrates the processes of adsorption separation, impurity removal treatment, evaporation concentration, crystallization and evaporation recovery, can be continuously and stably operated, and solves the problems of evaporation failure in the evaporation process and low purity and precipitation effect of a crystallized product.
In light of the foregoing description of the preferred embodiment of the present invention, many modifications and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.
Claims (3)
1. A magnesium sulfate crystallization separation process in CLT acid high-salt wastewater is characterized in that: comprises the following steps:
s1, performing nanofiltration adsorption separation on the CLT acid high-salt wastewater, and separating and recycling CLT acid macromolecular organic matters and partial intermediate products in the high-salt wastewater by adopting activated carbon and a nanofiltration membrane;
s2, converting the residual impurity ions in the separated wastewater into other precipitate substances by a chemical precipitation method;
s3, carrying out thermal evaporation concentration crystallization on the wastewater after the chemical precipitation treatment to obtain magnesium sulfate crystals with the average particle size of 294 mu m and the dispersion degree of 2; in the crystallization process, the stirring speed is increased, the turbulence degree of the system is increased, the metastable zone of the CLT acid high-salt wastewater is narrowed, and iron ions rich in the wastewater promote the precipitation of magnesium sulfate crystals;
s4, carrying out recrystallization treatment on the crystals subjected to thermal evaporation concentration to improve the purity, wherein in the recrystallization process, along with the increase of the stirring speed, the particle size of the product crystals is increased and then reduced and then tends to be stable; meanwhile, 3g/L of seed crystal is added to help to reduce the average particle size, and magnesium sulfate crystals with the particle size of 146 mu m and the dispersion of 1.42 and the purity of more than 96 percent are finally separated;
and S5, carrying out post-treatment recycling or putting the solvent doped with partial solute after concentration and crystallization into the system again.
2. The process for separating and crystallizing magnesium sulfate in CLT acid high-salt wastewater as claimed in claim 1, which is characterized in that: in step S3, the evaporation temperature during thermal evaporation and concentration is 60 ℃, the cooling rate is 0.2 ℃/min, the pH value is 3, and the rotation speed is 200 r/min.
3. The process for separating and crystallizing magnesium sulfate in CLT acid high-salt wastewater as claimed in claim 1, which is characterized in that: in the step S4, the concentration ratio adopted during recrystallization is 1.6, the residence time is 40min, the rotation speed is 200r/min, and the content of the seed crystal is 3 g/L.
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